The Portland daily press., 1887-11-19
THE MT. HAMILTON CLOCKS.
How the Time will be Kept at the
Great Lick Observatory.
rsan Jose, tcal.) Herald. ]

Dan JOSt, Vail tlcldu.l
One of the instruments at the Lick Obser-
vatory which the visitor to that institution
Justly regards with more than usual interest
is clock which stands just inside window
opening off from the main hall of the build
ing toward the west. This interest does not
arise from striking appearance of the clock,
for it is quite plainly mounted, but because
it has functions which seem to be so much
at variance with its surroundings Bolted
firmly to a heavy pier, in room where its
beats can scarcely be heard, even in the
solitude of that lonely mountain top, 1t regu-
lates the movements OF boats and railway
trains, and the endless variety of activities
from which rise the noise and hustle of busy
commercial life hundreds of miles away.
Clock making has been brought to such a
degree of perfection that clock which is
subject to variations of as much as the tenth
part of the second day is no longer consid-
cred first class. This is degree of accuracy
equivalent to the measurement of mile
with an error of not more than the sixteenth
of an inch. Even good watch is subject to
Irregularities very much greater than this.
The true test of tlmepiece is its perform
ance from day to day. and many watch
which Is claimed by its owner to have varied
not more than half a minute month, would
have been found guilty of greater errors If
1t had been examined frequently during the
The Lick Observatory has five standard
clocks by the best makers in the world.
They pass up through the floor of room
specially constructed for the purpose. with
double doors, windows and walls through
out. The piers are built on the solid rock Of
the mountain, and are entirely disconnected
from the building, so that no jar can be com
municated to the clocks. The double walls
of the room effectually guard against sudden
obo of QDrOn
are also kept here, two OF which are regular
ly used in connection with the time service.
In some observatories the clock room is stu
ated deep under ground, and the clocks are
even sealed up in alright cases, but the
equable climate at California renders this
unnecessary on Mt Hamilton.
Four of the observatory clocks keep side
real time, and are allowed to run without
regulation, their errors being allowed for;
the fifth is the standard mean time clock,
and is constantly adjusted, so as to be as
nearly right as possible every day at noon,
when time signals are transmitted to the
railroads. This is effected by means of
small weights of different sizes. The one
most used makes the clock gain tenth OF
a second per hour when placed on top of the
pendulum, and makes it lose the same
amount when placed on little shelf at the
bottom. 1t weighs 731 grains. The clock is
compared with one of the sldereal clocks
and two chronometers every day little be-
lore nine o CLOCK III tle nOIHlnS, anu mus
its error is determined. Then the weight is
applied, so as to correct the error before
noon.
If. for instance, the clock should be found
two-tenths of a second slow. the weight
would be on top of the pendulum and
removed at the end of two hours, when the
clock would be just right The pendulum is
of itself so nearly in adjustment that the
clock will run a day without getting more
than the tenth OF second out, and It is hard
ly ever necessary. to correct an error OIL as
much as two-tenths Of second: The rule
which has been adopted is to always have
the clock within tenth of a second at noon.
Another comparison with the two chron0m-
eters Immediately after the noon signals are
sent gives the precise amount OF error OF the
latter. The errors of the sidereal clocks are
determined by observation three times
There are other methods of regulating
clock without disturbing its pendulum, but
probably none are simpler and better than
this.
Having described the way in which the
standard clock is kept running on true time,
let us see by what means its signals are
transmitted to a distance.
Everybody nowadays knows that when a
telegraph operator taps his key the armature
of a magnet at distance station moves and
gives click, and that 1t is with an alphabet
composed of long and short clicks that he is
able to spell out words and transmit mes
sage. The electric pulse started by the de-
preston of the key travels along the tele-
graph wire with such enormous velocity that
the time required for its transmission over
ordinary distances is not appreciable.
Suppose telegraph operator to be seated
at the observatory in front of the standard
clock, where he can see its face, and to tap
his key at every second of the dial; then the
instruments in all telegraph offices connect
ed with the key by wires will give cores
bonding clicks, and if he distinguishes the
beginnings of the minutes and hours in any
way, say by making click double, or by
emitting it, the operators In the distant sta
lions can tell the exact time.
In the actual arrangement the operator in
front of the clock is dispensed with, and the
tapping of the key is done by the clock itself,
although the hand key is replaced by very
delicate pair of springs, so as to throw as
little work as possible on the clock. A wheel
originally with thirty teeth the thirtieth be-
ing cut away, is fixed on the arbol of the
second hand and lifts a spring at every even
second, except the ffty-eighth, making
magnet outside the clock room click Just as
if an operator were tapping his key at inter-
walls of two seconds, but emitting the last
click of every minute.
There is another wheel in the cleck which
causes five beats or ten seconds 10 be omit
ted before the beginning of every fifth min
ute The arrangement the clock ana OF
the outside machinery for transmitting time,
which need not be described here in detail,
is nearly the same as that used in the time
service of the observatory at Madison, Wis.,.
where it had been introduced and perfected
by Prof. Holden
The powerful electric current which Is
necessary TO send the signals over the long
telegraph line to San Jose is not let through
the clock, as it might injure the delicate ma
chine inside, but very feeble current Is en-
ployed to work the magnet outside, and this
in its turn starts at the same instant the
he Ion, Af
armature, just as if the latter were key
worked by hand. An electro-magnet so ar
ranged is called relay, name well known
to telegraph operators.
At the other end of the telegraph line lead
ing down the mountain, in the railroad office
of the Southern Pacific company in San Jose,
is large relay which is caused to beat by
the currents sent from the observatory in
this manner every two seconds. The obser-
vatory is responsible for the proper working
of this relay, but not for the transmission of
time signals beyond it. The instrument is
covered by glass case to exclude. the dust Of
the railway office.
Suppose that the reader is seated by his
relay at any time between nine a. M and six
D. M, and wishes to tell the exact time by
the observatory clock. He hears the instru-
ment beating at intervals of two seconds,
but this conveys no information to him.
Presently, however, comes pause, and one
beat is omitted. The next beat he knows be-
gins minute, but perhaps he has no way of
telling which one. He waits minute or
two longer and then comes long pause
five beats are omitted. He looks at his
watch and sees that the nearest even fifth
minute is, say twenty-five minutes past
eleven. At the next beat he can catch the
time exactly. To identify the minute after
the long pause, his watch must be less than
% minutes in error.
liz he does not know the time beforehand
to within p minutes, he may wait for the
noon signal, from which the railways get the
time. The noon signal is for the purpose of
identifying beyond the possibility of doubt
the twelve o'clock beat. 1t is not entirely
automatic, but requires the attention of the
observer on the mountain. At four minutes
before twelve the relay armature, which up
to that time had been beating as usual, be-
gins to rattle rapidly to and fro, and by the
following succession of long and short beats
to spell out the word time: -
-. This is repeated until three minutes
before twelve, when the beating stops, and q
long pause of one minute begins. The first
beat after this is two minutes of twelve and
the clock then beats regularly for two min
utes. The last ten seconds of the minute
before twelve are omitted, as usual, and the
next beat is exactly noon, After this the
clock is cut off, and the beating is not re-
sumed for several minutes.
The duty of the observatory ends here, bu
from this relay as a starting point the tim,
| signals are spread over the country in all di
| rections. The large relay is made to star
| simultaneously at every beat four differen
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